Epitaxial oxide fin segments to prevent strained semiconductor fin end relaxation

ABSTRACT

A method of forming a semiconductor device that includes providing regions of epitaxial oxide material on a substrate of a first lattice dimension, wherein regions of the epitaxial oxide material separate regions of epitaxial semiconductor material having a second lattice dimension are different than the first lattice dimension to provide regions of strained semiconductor. The regions of the strained semiconductor material are patterned to provide regions of strained fin structures. The epitaxial oxide that is present in the gate cut space obstructs relaxation of the strained fin structures. A gate structure is formed on a channel region of the strained fin structures separating source and drain regions of the fin structures.

BACKGROUND Technical Field

The present disclosure relates to fin structures, and more particularlyto fin structures including strained materials.

Description of the Related Art

The dimensions of semiconductor field effect transistors (FETs) havebeen steadily shrinking over the last thirty years or so, as scaling tosmaller dimensions leads to continuing device performance improvements.Planar FET devices typically have a conducting gate electrode positionedabove a semiconducting channel, and electrically isolated from thechannel by a thin layer of gate oxide. Current through the channel iscontrolled by applying voltage to the conducting gate. With conventionalplanar FET scaling reaching fundamental limits, the semiconductorindustry is looking at more unconventional geometries that willfacilitate continued device performance improvements. One such class ofdevice is a fin field effect transistor (FinFET). Further, strain basedenhancements have been contemplated for increasing carrier speeds insemiconductor devices.

SUMMARY

In one aspect, a method is provided for forming fin structures composedof strained semiconductor material. The method may include forming ahard mask on a semiconductor substrate of a first lattice dimension, andetching first openings into a first portion of the semiconductorsubstrate exposed by the hard mask. An epitaxial oxide having a secondlattice dimension than the first lattice dimension of the semiconductorsubstrate may then be formed in openings. A second portion of thesemiconductor substrate may then be etched using the epitaxial oxide asan etch mask to form second opening in the semiconductor substrate. Anepitaxial deposited semiconductor material having the second latticedimension that is different than the first lattice dimension may beformed in the second openings, wherein a difference between the firstlattice dimension and the second lattice dimension induces a strain inthe epitaxial deposited semiconductor material. Each region of epitaxialdeposited semiconductor material is patterned to provide fin structures.The epitaxial oxide is present in the fin cut space and obstructsrelaxation of the fin strain.

In another aspect, a method is provided for forming a semiconductordevice including fin structures having of a strained semiconductormaterial. In one embodiment, the method includes providing regions ofepitaxial oxide material formed on a substrate of a first latticedimension, wherein regions of the epitaxial oxide material separateregions of epitaxial semiconductor material having a second latticedimension different than the first lattice dimension to provide regionsof strained semiconductor. The regions of strained semiconductor arepatterned to provide regions of strained fin structures, wherein theepitaxial oxide is present in the fin cut space to obstruct relaxationof the strained fin structures. A gate structure is formed on a channelregion of the strained fin structures separating source and drainregions of the fin structures.

In another aspect of the present disclosure, a semiconductor device isprovided that includes a plurality of fin structures having a uniformstrain extending from edge to edge of each fin structure in saidplurality of fin structures. A gate structure is present on a channelregion of the fin structures having the uniform strain. Source and drainregions are formed on opposing sides of the channel region.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1A is a top down view depicting forming a fin cut mask on asemiconductor substrate having a first lattice dimension, in accordancewith one embodiment of the present disclosure.

FIG. 1B is a side cross-sectional view of the fin cut mask being formedon the semiconductor substrate that is depicted in FIG. 1A along sectionline B-B.

FIG. 2A is a top down view depicting etching a first portion of thesemiconductor substrate using the fin cut mask to form a first pluralityof openings that provide fin cut openings.

FIG. 2B is a side cross-sectional view depicting a side cross-sectionalview of the structure depicted in FIG. 2A along section line B-B.

FIG. 3A is a top down view depicting forming an epitaxial oxide in thefirst openings formed in the semiconductor substrate that provide thefin cut openings.

FIG. 3B is a side cross-sectional view of the structure depicted in FIG.3A along section line B-B.

FIG. 4 is a side cross-sectional view depicting removing the fin cutmask.

FIG. 5 is a side cross-sectional view depicting etching a second portionof the semiconductor substrate to provide a second plurality of openingsfor forming fin structures regions.

FIG. 6A is a top down view depicting forming an epitaxially depositedsemiconductor material formed in the second plurality of openings havinga second lattice dimension that is different than the first latticedimension of the semiconductor substrate.

FIG. 6B is a side cross-sectional view of the structure depicted in FIG.6A along section line B-B.

FIG. 7A is a top down view depicting patterning the regions of theepitaxially deposited semiconductor material to provide fin structures,in which the epitaxial oxide is present between the source and drainedges of adjacent fin structures to obstruct strain relaxation in thefin structures.

FIG. 7B is a side cross-sectional view depicting the structure depictedin FIG. 7A along section line B-B.

FIG. 8 is a side cross-sectional view depicting relaxation of the strainin fin structures when the epitaxial oxide is removed.

FIG. 9 is a side cross-sectional view depicting obstruction of thestrain relaxation in the fin structures that is provided by theepitaxial oxide being positioned in the fin cut space between adjacentfin structures.

FIG. 10A is a top down view of a FinFET including the strained finstructures and epitaxial oxide materials that are described withreference to FIGS. 1-9.

FIG. 10B is a side cross-sectional view of the structure depicted inFIG. 10A along section line B-B.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments is intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present disclosure. Forpurposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The terms “positioned on”means that a first element, such as a first structure, is present on asecond element, such as a second structure, wherein interveningelements, such as an interface structure, e.g. interface layer, may bepresent between the first element and the second element. The term“direct contact” means that a first element, such as a first structure,and a second element, such as a second structure, are connected withoutany intermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

The present disclosure is related to fin type field effect transistors,and other electrical devices including fin structures. A field effecttransistor (FET) is a semiconductor device in which output current,i.e., source-drain current, is controlled by the voltage applied to agate structure to the semiconductor device. A field effect transistorhas three terminals, i.e., gate structure, source region and drainregion. As used herein, a “fin structure” refers to a semiconductormaterial, which is employed as the body of a semiconductor device, inwhich the gate structure is positioned around the fin structure suchthat charge flows down the channel of the fin structure A FinFET is asemiconductor device that positions the channel region of thesemiconductor device in a fin structure. The source and drain regions ofthe fin structure are the portions of the fin structure that are onopposing sides of the channel region of the fin structure.

It has been determined that introducing strain to semiconductor devicescan increase carrier speed. For example, a compressive strain canincrease the speed of hole type carriers in p-type semiconductordevices, and a tensile strain can increase the speed of electron typecarriers in n-type semiconductor devices. In some embodiments,compressive and tensile strain can be produced in a semiconductor deviceby epitaxially growing the semiconductor material on a depositionsurface having a lattice dimension that is different from the epitaxialmaterial being formed.

It has been determined that in some examples, fin structures composed ofstrained semiconductor materials tend can partially relax or can fullyrelax when the fin structures are cut. More specifically, when a finstructure that is composed of a strained semiconductor material issections to provide two adjacent fin structures separated by a fin cutopening between the source/drain edges of a fin structure, the strainedsemiconductor material can experience relaxation. In some embodiments,the fin structures relax along their entirety, and in some embodiments,the fin structures relax at their edges. In the examples, in which thestrain entirely relaxes, the entire performance advantage that can beprovided by the strained materials is lost. In the examples when the finstructures relax at their edges, but maintain strain at their centralportions, there is an inconsistent strain profile that can also degradedevice performance.

In some embodiments, the methods and structures disclosed herein caneliminate the incidence of fin end relaxation after the fin cut bypositioning epitaxial oxide material in the regions where the fin cutwould occur. In some embodiments, by using the fin cut mask prior tostrained semiconductor formation on the silicon substrate, regions ofepitaxial oxide can be formed. The strained semiconductor material isthen grown around the epitaxial oxide. When fin structures are formedfrom the strained semiconductor material the fin now includes aepitaxial oxide segment, as opposed to a gap, in which the epitaxialoxide keeps the semiconductor fin end from relaxing. The effect can befurther enhanced by growing an epitaxial oxide lattice matched to thelattice constant of the strained semiconductor material. The methods andstructures disclosed herein, are now described in greater detail withreference to FIGS. 1A-10B.

FIGS. 1A and 1B depict forming a fin cut mask 5 on a semiconductorsubstrate 1 having a first lattice dimension. The semiconductorsubstrate 1 may be composed of any semiconductor material. For example,the semiconductor substrate 1 may be composed of a type IV or type III-Vsemiconductor material. By “type IV semiconductor” it is meant that thesemiconductor material includes at least one element from Group IVA(i.e., Group 14) of the Periodic Table of Elements. Examples of type IVsemiconductor materials that are suitable for the fin structure includesilicon (Si), germanium (Ge), silicon germanium (SiGe), silicon dopedwith carbon (Si:C), silicon germanium doped with carbon (SiGe:C) and acombination thereof. The semiconductor substrate may also be composed ofa type III-V semiconductor material, such as GaAs.

The term “lattice dimension”, also referred to as lattice constant, orlattice parameter, refers to the physical dimension of unit cells in acrystal lattice of a semiconductor material. For example, the latticedimension of silicon (Si) is 5.431 Å, and the lattice dimension forgermanium (Ge) is 5.65791 Å.

The fin cut mask 2 may be composed of a hard mask dielectric, and insome embodiments may be composed of a photoresist material. The term“fin cut” when used to describe the fin cut mask 2 refers to theposition of the mask relative to the later formed fin structures, inwhich the fin cut provides the space between the edges, i.e., ends ofthe source and drain region portions of the fin structures, that areadjacent and aligned fin structures. In the embodiments, in which thefin cut mask 2 is composed of a hard mask material, the dielectric usedfor the hard mask may be an oxide, nitride or oxynitride material. Forexample, the hard mask material that provides the fin cut mask 2 may besilicon nitride. The fin cut mask 2 may be formed using a depositionprocess to form the dielectric layer that is patterned usingphotolithography and etch processes. The material layer for the fin cutmask 2 may be blanket deposited using chemical vapor deposition, e.g.,plasma enhanced chemical vapor deposition (PECVD). The hard maskdielectric layer may then be patterned using photolithography and etchprocess to provide the geometry of the fin cut mask 2 that produces thefirst openings in the substrate 1, which can begin with forming aphotoresist block mask. A photoresist block mask can be produced byapplying a photoresist layer, exposing the photoresist layer to apattern of radiation, and then developing the pattern into thephotoresist layer utilizing conventional resist developer.

The portions of the hard mask dielectric layer that are protected by thephotoresist block mask remain to provide a fin cut mask 2 composed of ahard mask dielectric, and the portions of the dielectric layer that arenot protected by the photoresist block mask are removed by an etchprocess. The etch process for removing the exposed portions of the hardmask dielectric layer in patterning the fin cut mask 2 may be ananisotropic etch, such as reactive ion etch or laser etch, or anisotropic etch, such as a wet chemical etch.

Following formation of the fin cut mask 2, the exposed portions of thesemiconductor substrate 1 having the first lattice dimension may beetched, i.e., removed, to provide first openings 3, as depicted in FIGS.2A and 2B. In one embodiment, the etch process for etching thesemiconductor substrate 1 for forming the first openings 3 may be ananisotropic etch. An “anisotropic etch process” denotes a materialremoval process in which the etch rate in the direction normal to thesurface to be etched is greater than in the direction parallel to thesurface to be etched. One form of anisotropic etching that is suitablefor etching the first openings 3 into the semiconductor substrate 1 isreactive ion etching (RIE).

FIGS. 3A and 3B depict forming an epitaxial oxide 4 in the firstopenings formed in the semiconductor substrate 1 that provide the solidmaterial filling the fin cut openings, i.e., space, separating adjacentends of the subsequently formed fin structures, i.e., strained finstructures. The epitaxial oxide 4 may be selected to have a latticedimension substantially similar to the lattice dimension of the laterformed strained semiconductor material 6 that is epitaxially grown onthe semiconductor substrate 1.

In one example, the epitaxial oxide 4 is lanthanum (La) and oxygen (O)containing material, which has a lattice dimension that can be closelymatched to a silicon lattice. In one embodiment, the epitaxial oxide 4that is composed of lanthanum (La) and oxygen (O) can be a(La_(x)Y_(1-x))₂O₃ alloy. The epitaxial oxide 4 is lanthanum (La) andoxygen (O) containing material, e.g., (La_(x)Y_(1-x))₂O₃ alloy, may beepitaxially deposited. Other examples of epitaxial oxides that aresuitable for use as the epitaxial oxide 4 that is depicted being formedin FIGS. 3A and 3B can be selected from the group consisting of ceriumoxide (CeO₂), lanthanum oxide (La₂O₃), yttrium oxide (Y₂O₃), gadoliniumoxide (Gd₂O₃), europium oxide (Eu₂O₃), terbium oxide (Tb₂O₃) orcombinations thereof.

“Epitaxial growth and/or epitaxial deposition” means the growth of asemiconductor material on a deposition surface of a semiconductormaterial, in which the semiconductor material being grown hassubstantially the same crystalline characteristics as the semiconductormaterial of the deposition surface. The term “epitaxial material”denotes a semiconductor material that has substantially the samecrystalline characteristics as the semiconductor material that it hasbeen formed on, i.e., epitaxially formed on. In some embodiments, whenthe chemical reactants are controlled, and the system parameters setcorrectly, the depositing atoms of an epitaxial deposition processarrive at the deposition surface with sufficient energy to move aroundon the surface and orient themselves to the crystal arrangement of theatoms of the deposition surface. An epitaxial material has substantiallythe same crystalline characteristics as the semiconductor material ofthe deposition surface. For example, an epitaxial film deposited on a{100} crystal surface, e.g., the epitaxial oxide, will take on a {100}orientation.

In some embodiments, e.g., when the epitaxial oxide 4 is composed of alanthanum and oxygen containing material, e.g., metastable(La_(x)Y_(1-x))₂O₃ alloy, the epitaxial oxide 4 may be formed usingmolecular beam epitaxial (MBE) deposition. In MBE, material issublimated (or evaporated in the case of a liquid source) from effusioncells, thus forming molecular beams that are incident upon a heatedsample, i.e., deposition surface. In MBE, the molecules of the depositedmaterial land on the surface of the substrate, condense, and build upslowly and systematically, i.e., providing epitaxial growth.

In some embodiments, the epitaxial oxide 4 is deposited to a thicknessthat fills the first openings 3. In the embodiment depicted in FIGS. 3Aand 3B, the upper surface of the epitaxial oxide 4 may be substantiallycoplanar with the upper surface of the semiconductor substrate 1 thathas not been etched. In some embodiments, the height of the epitaxialoxide 4 may be selected to provide epitaxial oxide regions having aheight that will be substantially coplanar with the height of laterepitaxially formed strained semiconductor material 6 that provides thefin structures. This embodiment provides that an entire sidewall of thestrained fin structures is in contact with epitaxial oxide.

FIG. 4 depicts removing the fin cut mask 2. The fin cut mask 2 may beremoved using a selective etch process. As used herein, the term“selective” in reference to a material removal process denotes that therate of material removal for a first material is greater than the rateof removal for at least another material of the structure to which thematerial removal process is being applied. For example, in oneembodiment, a selective etch may include an etch chemistry that removesa first material selectively to a second material by a ratio of 100:1 orgreater. The fin cut mask 2 may be removed using an etch that isselective to the epitaxial oxide 4, and in some embodiments theunderlying semiconductor substrate 1.

FIG. 5 depicts etching a second portion of the semiconductor substrate 1to provide a second plurality of openings 5 for forming regions of finstructures. The etch process depicted in FIG. 5 can employ the epitaxialoxide 4 as an etch mask. The etch process for forming the secondopenings 5 may be a selective etch process, i.e., an etch process thatis selective to the epitaxial oxide. The etch process can be ananisotropic etch process, such as reactive ion etch. The depth by whichthe exposed portions of the semiconductor substrate 1 is etched toprovide the second openings 5 can be selected to dictate the height ofthe later formed fin structures, as the recessed surfaces of the secondopenings 5 may provide the epitaxial growth surface of the epitaxiallydeposited semiconductor material that is processed to provide thestrained fin structures.

FIGS. 6A and 6B depict forming an epitaxially deposited semiconductormaterial 6 formed in the second plurality of openings 5 having a secondlattice dimension that is different than the first lattice dimension ofthe semiconductor substrate 1, wherein the epitaxially depositedsemiconductor material 6 is formed with an intrinsic strain that resultsfrom the difference in lattice dimensions of the two interfacingmaterials. For example, in embodiments, in which the epitaxiallydeposited semiconductor material 6 is composed of a silicon andgermanium containing semiconductor that is epitaxially formed on asemiconductor substrate 1 that is composed of silicon (Si), the largerlattice constant of the epitaxially deposited semiconductor material 6in epitaxial relationship with smaller deposition surface provided bythe silicon (Si) semiconductor substrate will result in the epitaxiallydeposited semiconductor material 6 having a compressive strain.

In some embodiments, the content of the epitaxial oxide 4, and theepitaxially deposited semiconductor material 6, is selected so that thelattice dimensions substantially match. In some embodiments, theepitaxially deposited semiconductor material 6 may be silicon germanium(SiGe) having a germanium (Ge) content ranging from 15 wt. % to lessthan 30 wt. %. In other embodiments, the germanium (Ge) of the silicongermanium (SiGe) that provides the epitaxially deposited semiconductormaterial 6 content ranges from 15 wt. % to 25 wt. %. In one example, thegermanium content in the silicon germanium (SiGe) that provides theepitaxially deposited semiconductor material 6 is equal to 20 wt. %.Turning to the epitaxial oxide 4, in some embodiments, when usingyttrium/lanthanum-oxide based systems, such as (La_(x)Y_(1-x))₂O₃, theyttrium has to be the majority compound to ensure that a cubic latticeis formed. For example, the cubic lattice of the yttrium/lanthanum-oxidebased systems matches well with the Si/SiGe lattice. In someembodiments, when the epitaxially deposited semiconductor material 6 iscomposed of silicon (Si) and germanium (Ge), the La—Y-oxide basedinterlayer system is only suitable for use with silicon germanium (SiGe)material having a germanium (Ge) content of 25 at. % or less. Othercombinations of materials and compositions for the epitaxial oxide 4 andthe epitaxially deposited semiconductor 6 are also possible. Forexample, the epitaxially deposited semiconductor material 6 may be anymaterial that can be formed on the exposed surface of the semiconductorsubstrate 1. Epitaxial oxides might include a rare earth oxide. The rareearth oxide may include binary oxides, such as, e.g.,gadolinium(III)-oxide (Gd₂O₃), dysprosium(III)-oxide (Dy₂O₃),holmium(III) oxide (Ho₂O₃), erbium (III) oxide (Er₂O₃), thulium (III)oxide (Tm₂O₃), lutetium(III) oxide (Lu₂O₃) or cerium (IV) oxide (CeO₂),etc. or ternary oxides including a rare earth metal, such as e.g., Gd,Er, Nd, La and Y forming oxides such as, e.g., lanthanum-yttrium oxide((La_(x)Y_(1-x))₂O₃), gadolinium-erbium oxide ((Gd_(x)Er_(1-x))₂O₃),neodymium-erbium oxide ((Nd_(x)Er_(1-x))₂O₃), neodymium-gadolinium oxide((Nd_(x)Gd_(1-x))₂O₃), lanthanum-erbium oxide ((La_(x)Er_(1-x))₂O₃), andcombinations thereof.

For example, in addition to silicon germanium (SiGe), the epitaxialdeposited semiconductor material 6 can be any type IV and/or type III-Vsemiconductor material. It is noted that silicon germanium (SiGe) formedon a silicon (Si) semiconductor substrate 1 provides an epitaxiallydeposited semiconductor material 6 having a compressive strain. Similarresults can be produced by employing a germanium (Ge) epitaxiallydeposited semiconductor material 6 that is formed on a silicon (Si)semiconductor substrate 1; or a silicon germanium (SiGe) epitaxiallydeposited semiconductor material 6 that is epitaxially formed on asilicon germanium (SiGe) semiconductor substrate 1, in which thegermanium (Ge) content in the epitaxially deposited semiconductormaterial 6 is greater than the germanium (Ge) content in thesemiconductor substrate 1. In some embodiments, to provide a epitaxiallydeposited semiconductor material 6 that has an intrinsic tensile strain,the composition of the epitaxially deposited semiconductor material 6 isselected to have a lesser a lattice dimension than the surface on whichthe epitaxially deposited semiconductor material is formed. No-nobodywill use Si:C as channel material, since the carbon kills mobility. Inother embodiments, to provide a tensile strained material for providingfin structures, the epitaxially deposited semiconductor material 6 maybe composed of silicon (Si), while the semiconductor substrate 5 iscomposed of germanium (Ge) or silicon germanium (SiGe). In yet anotherembodiment, to provide a tensile strained material, the epitaxiallydeposited semiconductor material 6 may be composed of silicon andgermanium, e.g., silicon germanium (SiGe), and the semiconductorsubstrate 1 may be composed of silicon and germanium, e.g., silicongermanium (SiGe), in which the germanium content in the epitaxialdeposited semiconductor material 6 may be less than the germaniumcontent of the semiconductor substrate 1.

The epitaxially deposited semiconductor material 6 may be formed using achemical vapor deposition apparatus (CVD), such as plasma enhancedchemical vapor deposition (PECVD), metal organic chemical vapordeposition (MOCVD), atmospheric pressure CVD (APCVD), low pressure CVD(LPCVD) and combinations thereof. A number of different sources may beused for the deposition of the epitaxially deposited semiconductor. Insome embodiments, a germanium gas source may be selected from the groupconsisting of germane (GeH₄), digermane (Ge₂H₆), halogermane,dichlorogermane, trichlorogermane, tetrachlorogermane and combinationsthereof. Silicon sources for deposition may be selected from the groupconsisting of silane, disilane, trisilane, tetrasilane,hexachlorodisilane, tetrachlorosilane, dichlorosilane, trichlorosilane,and combinations thereof. We don't have carbon.

FIGS. 7A and 7B depicting patterning the regions of the epitaxiallydeposited semiconductor material 6 to provide fin structures 7, in whichthe epitaxial oxide 4 is presents between the source and drain edges ofadjacent fin structures 7 to obstruct strain relaxation in the finstructures 7.

In one embodiment, the patterning process used to define each of the finstructures 7 is a sidewall image transfer (SIT) process. The SIT processcan include forming a mandrel material layer (not shown) on theepitaxially formed semiconductor material 6 that provides the finstructures 7. The mandrel material layer can include any material(semiconductor, dielectric or conductive) that can be selectivelyremoved from the structure during a subsequently performed etchingprocess. In one embodiment, the mandrel material layer may be composedof amorphous silicon or polysilicon. In another embodiment, the mandrelmaterial layer may be composed of a metal, such as, e.g., aluminum (Al),tungsten (W), or copper (Cu). The mandrel material layer can be formedby a deposition method, such as chemical vapor deposition or plasmaenhanced chemical vapor deposition. In one embodiment, the thickness ofthe mandrel material layer can be from 50 nm to 300 nm. Followingdeposition of the mandrel material layer, the mandrel material layer canbe patterned by lithography and etching to form a plurality of mandrelstructures on the topmost surface of the semiconductor containingmaterial that provides the fin structures 7.

In some embodiments, the SIT process may continue by forming adielectric spacer on each sidewall of each mandrel structure. Thedielectric spacer can be formed by deposition of a dielectric spacermaterial, and then etching the deposited dielectric spacer material. Thedielectric spacer material may comprise any dielectric spacer materialsuch as, for example, silicon dioxide, silicon nitride or a dielectricmetal oxide. Examples of deposition processes that can be used inproviding the dielectric spacer material include, but are not limitedto, chemical vapor deposition (CVD), plasma enhanced chemical vapordeposition (PECVD), or atomic layer deposition (ALD). Examples ofetching that be used in providing the dielectric spacers include anyetching process such as, e.g., reactive ion etching (RIE). Since thedielectric spacers are used in the SIT process as an etch mask, thewidth of the each dielectric spacer determines the width of each finstructure 7.

In some embodiments, after formation of the dielectric spacers, the SITprocess continues by removing each mandrel structure. Each mandrelstructure can be removed by an etching process that is selective forremoving the mandrel material as compared to silicon. Following themandrel structure removal, the SIT process continues by transferring thepattern provided by the dielectric spacers into the semiconductormaterial layer that provides the fin structures 7, such as the SOI layerof an SOI substrate. The pattern transfer may be achieved by utilizingat least one etching process that can include dry etching, such asreactive ion etching (RIE), plasma etching, ion beam etching or laserablation, chemical wet etch processes or a combination thereof. In oneexample, the etch process used to transfer the pattern may include oneor more reactive ion etching (RIE) steps. The etching steps pattern thesemiconductor material layer to provide the fin structures 7. Followingetching, i.e., pattern transfer, the SIT process may conclude withremoving the dielectric spacers using an etch process or a planarizationprocess.

Each of the fin structures 7 may have a height ranging from 5 nm to 200nm. In another embodiment, each of the fin structures 7 has a heightranging from 10 nm to 100 nm. In one example, each of the fin structures7 has a height ranging from 20 nm to 50 nm. It is noted that the heightof the fin structures 7 may be equal to the height of the epitaxialoxide 4. Each of the plurality of fin structures 7 may have a width ofless than 20 nm. In another embodiment, each of the fin structures 7 hasa width ranging from 3 nm to 8 nm. The pitch P1 separating adjacent finstructures 7 may range from 35 nm to 45 nm. In another example, thepitch separating adjacent fin structures 7 may range from 30 nm to 40nm.

FIG. 8 depicts relaxation of the strain in the fin structures 4 that hasbeen discovered if the epitaxial oxide 4 is not present filling the fincut opening. The fin cut opening is the space between the edges, i.e.,the outermost edge of the source/drain regions portions of the finstructures, which is separating adjacent fin structures 4. This space,i.e., the fin cut space, has length dimension, i.e., the dimension fromone edge of a first fin structure to an edge of second adjacent finsstructure, that is perpendicular to the dimension that defines the pitchP1 between adjacent fin structures 7. The length of the fin cutdimension is depicted in the supplied figures as FC1.

As illustrated in FIG. 8, freestanding strained semiconductor finstructures 7′, such as those having a height on the order of 40 nm to 60nm, typically experience strain relaxation in the directions illustratedby arrows having reference number 11. This strain relaxation isdepicted, although an exaggeration, with the deformation of thesidewalls of the fin structures 7′ after the fin cut FC1 etch thatremoves a portion of the fin structure to provide two adjacent finstructures 7′ separated by a fin cut gap. Because, there is nothingwithin the fin cut gap to confine the fin edge structures fromdeformation that results from the intrinsic strain produced by thedifference in lattice dimensions between the epitaxially formed finstructure material and the underlying growth surface, i.e.,semiconductor substrate 1, the structures can deform as the strainrelaxes typically at the fin edges, and in some examples across theentirety of the fin structure 7′.

FIG. 9 illustrates how in some embodiments, the epitaxial oxide 4 thatis present in the fin cut gap FC1 prior to fin patterning, as describedin FIGS. 7A-7B, and after fin patterning, obstructs strain relaxation.For example, the epitaxial oxide 4 can confine the strained epitaxialsemiconductor material 6 during growth, and can maintain or enhance thestrain in the strained semiconductor fin 7 after the fin cut, becausethe epitaxial oxide 4 obstructs any deformation of the fin structures 7that typically would occur if the epitaxial oxide 4 was not present inthe fin cut opening between adjacent fin structures 7. As depicted inFIG. 9, there is no deformation of the edges of the fin structures 7when the epitaxial oxide is present in the fin cut gap.

FIGS. 10A and 10B depict a FinFET including the strained fin structures7 and epitaxial oxide materials 10 that are described with reference toFIGS. 1-9. The FinFET devices depicted in FIGS. 10A and 10B are onlyformed on a portion of the fin structures 7 depicted in FIGS. 1-9. Thesemiconductor device may include a plurality of fin structures 7 havinga uniform strain extending from edge E1 to edge E2 of each finstructure. An epitaxial oxide 4 may be present in the fin cut openingpresent between edges E1, E2 of said plurality of fin structures 7. Agate structure 8 may be present on a channel region of the finstructures 7. A source region 15, and drain region 20 may be formed onportions of the fin structure 7 that are on opposing sides of thechannel region.

The “gate structure” functions to switch the semiconductor device froman “on” to “off” state, and vice versa. The gate structure 8 are formedon the channel region of each the fin structures 7 that will beprocessed to form semiconductor devices, e.g., FinFETs. The gatestructure 8 typically includes at least a gate dielectric 21 that ispresent on the channel region of the fin structure 7, and a gateelectrode 22 that is present on the gate dielectric 21. In oneembodiment, the at least one gate dielectric layer 21 includes, but isnot limited to, an oxide, nitride, oxynitride and/or silicates includingmetal silicates, aluminates, titanates and nitrides. In one example,when the at least one gate dielectric layer 21 is comprised of an oxide,the oxide may be selected from the group including, but not limited to,SiO₂, HfO₂, ZrO₂, Al₂O₃, TiO₂, La₂O₃, SrTiO₃, LaAlO₃, Y₂O₃ and mixturethereof. The physical thickness of the at least one gate dielectriclayer 21 may vary, but typically, the at least one gate dielectric layer21 has a thickness from 1 nm to 10 nm. In another embodiment, the atleast one gate dielectric layer 21 has a thickness from 1 nm to 3 nm.

The conductive material of the gate electrode 22 may comprisepolysilicon, SiGe, a silicide, a metal or a metal-silicon-nitride suchas Ta—Si—N. Examples of metals that can be used as the gate electrode 22include, but are not limited to, Al, W, Cu, and Ti or other likeconductive metals. The layer of conductive material for the gateelectrode 22 may be doped or undoped. If doped, an in-situ dopingdeposition process may be employed. Alternatively, a doped conductivematerial can be formed by deposition, ion implantation and annealing.

The gate structure 8 may be formed by using a deposition method, such asa chemical vapor deposition method and/or a physical vapor deposition(PVD), to deposit the material layers for the at least one gatedielectric layer and the at least one gate electrode followed byphotolithography and etch processing.

Still referring to FIGS. 10A and 10B, a gate sidewall spacer 9 may beformed on the sidewalls of the gate structure 8. The gate sidewallspacer 9 may be composed of a dielectric material, such as siliconnitride, and is formed using deposition processes, such as chemicalvapor deposition, followed by etch back processes, such as reactive ionetch (RIE).

In a following process step, the source and drain regions 20, 25 may beformed on the source and drain regions portions of the fin structures 7that are present on opposing sides of the channel region of the finstructures 7.

FIGS. 10A and 10B depict forming doped epitaxial semiconductor materialon the source and drain portions of the fin structures 7. The epitaxialmaterial formed on the fin structures of Fin Field Effect Transistors(FinFET) may provide a component of the source and drain regions 20, 25of the FinFET. In this example, the epitaxial semiconductor material maybe formed on the source and drain region 20, 25 portions of the finstructures 10, which are on opposing sides of the channel portion of thefin structure 10 that the gate structure 15 is present on.

In some embodiments, the epitaxial semiconductor material for the sourceand drain regions 20, 25 may be composed of silicon (Si), germanium(Ge), silicon germanium (SiGe), silicon doped with carbon (Si:C) or theepitaxial semiconductor material 30 may be composed of a type III-Vcompound semiconductor, such as gallium arsenide (GaAs). The epitaxialsemiconductor material that provides the source and drain regions 20, 25may be in situ doped to a p-type or n-type conductivity. The term “insitu” denotes that a dopant, e.g., n-type or p-type dopant, isintroduced to the base semiconductor material, e.g., silicon or silicongermanium, during the formation of the base material. For example, an insitu doped epitaxial semiconductor material may introduce n-type orp-type dopants to the material being formed during the epitaxialdeposition process that includes n-type or p-type source gasses. In theembodiments in which the FinFET device being formed has n-type sourceand drain regions 20, 25, and is referred to as an n-type FinFET, thedoped epitaxial semiconductor material is doped with an n-type dopant tohave an n-type conductivity. In the embodiments in which the FinFETdevice being formed has p-type source and drain regions 20, 25, and isreferred to as a p-type FinFET, the doped epitaxial semiconductormaterial is doped with a p-type dopant to have a p-type conductivity. Asused herein, “p-type” refers to the addition of impurities to anintrinsic semiconductor that creates deficiencies of valence electrons.In a type IV semiconductor, such as silicon, examples of p-type dopants,i.e., impurities, include but are not limited to, boron, aluminum,gallium and indium. As used herein, “n-type” refers to the addition ofimpurities that contributes free electrons to an intrinsicsemiconductor. In a type IV semiconductor, such as silicon, examples ofn-type dopants, i.e., impurities, include but are not limited toantimony, arsenic and phosphorous.

In one embodiment, the n-type gas dopant source may include arsine(AsH₃), phosphine (PH₃) and alkylphosphines, such as with the empiricalformula R_(x)PH_((3-x)), where R=methyl, ethyl, propyl or butyl and x=1,2 or 3. Alkylphosphines include trimethylphosphine ((CH₃)₃P),dimethylphosphine ((CH₃)₂PH), triethylphosphine ((CH₃CH₂)₃P) anddiethylphosphine ((CH₃CH₂)₂PH). The p-type gas dopant source may includediborane (B₂H₆). In some embodiments, the n-type or p-type dopant may bepresent in the doped epitaxial semiconductor material of the source anddrain regions 20, 25 in a concentration ranging from 1×10²⁰ to 5×10²¹atoms/cm³. In another embodiment, the n-type or p-type dopant may bepresent in the doped epitaxial semiconductor material of the source anddrain regions 20, 25 in a concentration ranging from 4×10²⁰ to 2×10²¹atoms/cm³.

It is noted that the source and drain regions 20, 25 of differentsemiconductor devices in different regions of the substrate may beindividually processed using block masks. This can provide n-type andp-type semiconductor devices on the same semiconductor substrate 1.

In one embodiment, dopant from the doped epitaxial semiconductormaterial of the source and drain regions 20, 25 is diffused into theunderlying portions of the fin structures 7 to form extension dopantregions. In some embodiments, the diffusion, i.e., driving, of thedopant from the doped epitaxial semiconductor material 30 into theextension region portions of the fin structures 10 comprises thermalannealing. In one embodiment, the thermal annealing that diffuses thedopant from the doped epitaxial semiconductor material 30 into theextension region portions of the fin structures 10 includes an annealingprocess selected from the group consisting of rapid thermal annealing(RTA), flash lamp annealing, furnace annealing, laser annealing andcombinations thereof.

As noted above, the FinFETs depicted in FIGS. 10A and 10B can be formedhaving strained fin structures 7, in which the strain present in the finstructures 7 can increase carrier speeds. For example, a fin structure 7composed of silicon germanium (SiGe) that is epitaxially formed on asemiconductor substrate 1 of silicon (Si) and having epitaxial oxideregions 4 of yttrium/lanthanum-oxide based systems, such as(La_(x)Y_(1-x))₂O₃, present in the fin cut openings separating the edgesof adjacent fin structures 7 may have a compressive strain thatincreases carrier speeds in p-type semiconductor devices. The germaniumcontent of the silicon germanium in the fin structure 7 may be as greatat 25 at. %. It is noted that other strained semiconductor materials andepitaxial oxides 4 are suitable for use with the present disclosure. Forexample, the epitaxial oxide 4 may also be composed of, in someembodiments, when using yttrium/lanthanum-oxide based systems, such as(La_(x)Y_(1-x))₂O₃, the yttrium has to be the majority compound toensure that a cubic lattice is formed. For example, the cubic lattice ofthe yttrium/lanthanum-oxide based systems matches well with the Si/SiGelattice. In some embodiments, when the epitaxially depositedsemiconductor material 6 is composed of silicon (Si) and germanium (Ge),the La—Y-oxide based interlayer system is only suitable for use withsilicon germanium (SiGe) material having a germanium (Ge) content of 25at. % or less. Other combinations of materials and compositions for theepitaxial oxide 4 and the epitaxially deposited semiconductor 6 are alsopossible. For example, the epitaxially deposited semiconductor material6 may be any material that can be formed on the exposed surface of thesemiconductor substrate 1. Epitaxial oxides might include a rare earthoxide. The rare earth oxide may include binary oxides, such as, e.g.,gadolinium(III)-oxide (Gd₂O₃), dysprosium(III)-oxide (Dy₂O₃),holmium(III) oxide (Ho₂O₃), erbium (III) oxide (Er₂O₃), thulium (III)oxide (Tm₂O₃), lutetium(III) oxide (Lu₂O₃) or cerium (IV) oxide (CeO₂),etc. or ternary oxides including a rare earth metal, such as e.g., Gd,Er, Nd, La and Y forming oxides such as, e.g., lanthanum-yttrium oxide((La_(x)Y_(1-x))₂O₃), gadolinium-erbium oxide ((Gd_(x)Er_(1-x))₂O₃),neodymium-erbium oxide ((Nd_(x)Er_(1-x))₂O₃), neodymium-gadolinium oxide((Nd_(x)Gd_(1-x))₂O₃), lanthanum-erbium oxide ((La_(x)Er_(1-x))₂O₃), andcombinations thereof. In some embodiments, the compressive strain may beequal to 200 MPa to 3 GPa. In another example, the fin structure 7 maybe strained to have a tensile strain that ranges from 200 MPa to 3 GPa.

The semiconductor device may include a plurality of fin structures 7having a uniform strain extending from edge E1 to edge E2 of each finstructure 7. By uniform strain it is meant that the amount of strain atthe edges E1, E2 and the channel region of the fin structure 7, i.e.,the portion of the fin structure 7 underlying the gate region 8, issubstantially the same. The same is true of each point of the finstructure between the edges E1, E2 and the channel region. As describedabove, the uniform strain results from the present of epitaxial oxide 4in direct contact with the edges E1, E2 separating adjacent finstructures 7. The epitaxial oxide 4 may be present in the fin cutopening, e.g., filling an entirety of the fin cut opening, that ispresent between the edges E1, E2 of said plurality of fin structures 7.

It is noted that the above process sequence describes a gate firstprocess sequence for forming FinFETs. The present disclosure is notlimited to only gate first processing. For example, gate last, which isalso referred to as replacement gate processing, is also suitable foruse with the methods and structures of the present disclosure. A gatelast process can include forming a replacement gate structure on thechannel portion of the fin structures, forming a spacer on the sidewallof the replacement gate structure, forming source and drain regions onopposing sides of the replacement gate structure, removing thereplacement gate structure, and forming a functional gate structure inthe space once occupied by the replacement gate structure. Thereplacement gate structure can include sacrificial material that definesthe geometry of a later formed functional gate structure that functionsto switch the semiconductor device from an “on” to “off” state, and viceversa. A process sequence employing a replacement gate structure may bereferred to as a “gate last” process sequence. Both gate first and gatelast process sequences are applicable to the present disclosure.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

While the methods and structures of the present disclosure have beenparticularly shown and described with respect to preferred embodimentsthereof, it will be understood by those skilled in the art that theforegoing and other changes in forms and details may be made withoutdeparting from the spirit and scope of the present disclosure. It istherefore intended that the present disclosure not be limited to theexact forms and details described and illustrated, but fall within thescope of the appended claims.

What is claimed is:
 1. A structure comprising: a plurality of finstructures having a strain extending from edge to edge of each finstructure in said plurality of fin structures; and an epitaxial oxidepresent in an opening present between edges of said plurality of finstructures, wherein epitaxial oxide prevents said strain in saidplurality of fin structures from relaxing.
 2. The structure of claim 1,wherein the plurality of fin structures are present on a substratehaving a different lattice dimension than a lattice dimension for thefin structures.
 3. The structure of claim 1, wherein each of theplurality of fin structures comprise silicon, germanium, silicongermanium or a combination thereof,
 4. The structure of claim 1, whereinthe epitaxial oxide is a rare earth oxide composition.
 5. The structureof claim 1, wherein the epitaxial oxide is selected from the groupconsisting of cerium oxide (CeO₂), lanthanum oxide (La₂O₃), yttriumoxide (Y₂O₃), gadolinium oxide (Gd₂O₃), europium oxide (Eu₂O₃), terbiumoxide (Tb₂O₃) and combinations thereof.
 6. The semiconductor device ofclaim 1, wherein the strain is a compressive strain.
 7. The structure ofclaim 1, wherein the strain is a tensile strain.
 8. The structure ofclaim 1, wherein the epitaxial oxide is (La_(x)Y_(1-x))₂O₃.
 9. Thestructure of claim 1, wherein the fin structures are comprised ofsilicon germanium (SiGe).
 10. The structure of claim 9, wherein thesilicon germanium comprises 20 wt. % to 25 wt. % germanium (Ge).
 11. Asemiconductor device comprising: a plurality of fin structures having auniform strain extending from edge to edge of each fin structure in saidplurality of fin structures; a rare earth oxide composition comprisingpresent in a gate cut opening present between edges of said plurality offin structures; and a gate structure present on a channel region of thefin structures having the uniform strain, wherein the rare earth oxideprevents said strain in said plurality of fin structures from relaxing.12. The semiconductor device of claim 11, wherein the fin structures arepresent on a substrate having a different lattice dimension than alattice dimension for the fin structures.
 13. The semiconductor deviceof claim 11, wherein the fin structures comprise silicon, germanium,silicon germanium or a combination thereof,
 14. The semiconductor deviceof claim 11, wherein the rare earth oxide is selected from the groupconsisting of cerium oxide (CeO₂), lanthanum oxide (La₂O₃), yttriumoxide (Y₂O₃), gadolinium oxide (Gd₂O₃), europium oxide (Eu₂O₃), terbiumoxide (Tb₂O₃) and combinations thereof.
 15. The semiconductor device ofclaim 11, wherein the uniform strain is a compressive strain.
 16. Thesemiconductor device of claim 11, wherein the uniform strain is atensile strain.
 17. The semiconductor device of claim 11, wherein theepitaxial oxide is (La_(x)Y_(1-x))₂O₃.
 18. The semiconductor device ofclaim 11, wherein the fin structures are comprised of silicon germanium(SiGe).
 19. The semiconductor device of claim 18, wherein the silicongermanium comprises 20 wt. % to 25 wt. % germanium (Ge).
 20. Thestructure comprising: a plurality of fin structures comprising silicongermanium having a compressive strain extending from edge to edge ofeach fin structure in said plurality of fin structures; and lanthanumoxide present in an opening present between edges of said plurality offin structures, wherein the lanthanum oxide prevents said strain in saidplurality of fin structures from relaxing.